It is somewhat true that no buildings are the same, but there are some general rules that can be applied to gas detection systems for a given application.
Interserv provides service for almost any given application. We are fully equipped to service all kind of fixed gas detection systems, please see below for some examples:
Applications
Parking/Service Garages
Most mechanical building codes indicate that ventilation for parking structures should be continuous, 24/7, unless a system is in place to ensure hazardous gas concentrations are kept below prescribed levels. By ventilating only when sensors indicate a requirement, there is an opportunity for very significant energy savings, both from reduced fan operation, and potentially also from any related heating or cooling costs.
For gasoline, natural gas, or propane powered vehicles, carbon monoxide (CO) is the primary gas of concern. For gas detection applications in which diesel engines are employed, nitrogen dioxide (NO2) should also be measured to ensure adequate coverage.
Vehicle exhaust presents an interesting challenge when designing a gas detection system. Because of the wide variety of applications including underground parking garages, bus barns, maintenance facilities, tunnels, train stations, airports, loading docks, car and truck dealerships and warehouses, a number of different gas detection solutions exist to satisfy the varying requirements. Therefore a number of factors must be taken into consideration when determining what type of system should be specified.
According to Ontario’s Building Code, if a monitoring system is not installed within an area where a gas like CO is present, an exhaust fan is required with nonstop operation 24 hours a day for a “continuous supply of outdoor air”. It is also a violation of the code to have fans setup on a cycle or to shut them off at any time as:
Section 6.2.2.3 of the Ontario Building Code States:
- (1) Enclosed storage garage shall have a mechanical ventilation system designed to:
(a) limit the concentration of carbon monoxide to not more than 100 parts per million of air when measured between 900 mm and 1800 mm from the floor.
(b) Provide, during operating hours, a continuous supply of outdoor air at a rate of not less than 3.9 L/s for each square metre of floor area.
- (2) Mechanical ventilation systems provided in accordance with Clause (1)(a) shall be controlled automatically by carbon monoxide monitoring devices, located so as to provide full protection throughout the storage garage
Mechanical/Chiller Rooms
The release of refrigerant gases into the environment can be harmful to both the potential occupants of the space, as well as to the environment in general. Chlorofluorocarbons, commonly known as CFCs, which were formerly considered relatively safe, are now known to be a key contributor to the thinning of the ozone layer. These are gradually being replaced by more environmentally friendly refrigerants such as R134a. This however, does not lessen the need for leak detection. Regardless of their reduced impact on the environment, even modern refrigerants pose the risk of displacing the oxygen in mechanical/chiller rooms, should a leak occur.
Mechanical Refrigeration Code B-52 – 6.2.3
- Each refrigerating machinery room shall contain a detector located in an area where a refrigerant leak will most likely to concentrate and shall be actuated at a value not greater than the corresponding TLV®/TWA
- The detector, when activated, shall sound a sufficiently audible alarm; and initiate mechanical ventilation
- Readily accessible independent fan switches shall be installed inside and outside the machinery room. Fan switches located outside the machinery room shall be capable of starting but not stopping the ventilation.
- At each entrance point to the refrigerating room there should be audio & visual annunciation.
Maintenance of Systems Code B-52 – 8.4.1
- (d) Leak detectors shall be tested for function at the specified refrigerant concentration in accordance with the manufacturer’s instructions. The maximum interval between tests shall not exceed one year. The leak detector, in the simulated leak test, shall initiate an audible and visual alarm and begin ventilation of a rate not less than specified in 6.2.5.5. Failure of any of the three functions shall require corrective action.
General Recommendations
In some applications, solid-state sensing technology will provide economical leak detection for most refrigerants. If however, there are other gases in the background in the area or multiple refrigerant types, infrared technology, which is very specific to the particular refrigerant being used, is a more suitable choice.
For most refrigerants, gas sensors should be mounted close to the floor, in close proximity to probable leak sources, and where pooled refrigerant is likely to accumulate. Recommended coverage radius for an individual sensor is approx. 20 ft.
Ammonia is used as a refrigerant primarily in applications requiring very low temperatures such as food processing or ice arenas. Electro-chemical sensors are required to ensure accurate monitoring at regulatory levels. In ammonia gas detection applications, sensors should be mounted at or near the ceiling.
Battery Rooms
As lead acid batteries are charged, minute quantities of hydrogen (H2) gas are produced.
Normally, the amount of hydrogen generated during charging is not of a sufficient quantity to cause concern. There are instances however, where for various reasons, hydrogen may accumulate to create potentially hazardous gas conditions.
Battery back-up installations for equipment such as telephone switching systems and computers are normally situated in small rooms with little ventilation. This confined space provides an excellent opportunity for hydrogen to accumulate and reach combustible levels.
In most instances, the sensor/transmitter is mounted on the ceiling, while the monitoring panel is mounted outside the room. Any build-up will cause an alarm and/or initiate ventilation.
A second common application is in warehouses where battery powered forklifts are used. Charging stations are commonly lined up in areas where a large number of vehicles can be charged simultaneously. Because of the size and number of batteries, dangerous levels of H2 can accumulate.
Key Factors:
- Relative density of hydrogen is 0.069. Therefore sensors should be mounted at or near the ceiling, away from any source of fresh air, which may dilute the sample.
- Remote sensors are normally used, with panels being mounted away from hydrogen source.
Waste Water Treatment
Growing environmental concerns have resulted in the construction and upgrading of waste water treatment plants throughout North America.
By their very design, processes involved in sewage treatment produce and use a number of highly toxic and explosive gases, requiring waste water monitoring to ensure the safety of both employees and the environment.
There are three main gases to be aware of when designing monitoring systems for waste water treatment facilities.
Hydrogen Sulfide: A highly toxic gas (TLV 10 PPM) produced wherever large holding tanks or settling basins are located. Because few of these areas conform to normal square footage guidelines, sensors are located as required near probable H2S sources.
Methane: Also known as natural gas, methane is an explosive gas (L.E.L 5% volume) produced primarily in the initial stages of decomposition. Because of its low density, methane will accumulate in pockets near the ceiling of enclosed areas such as holding tanks and settling basins.
Oxygen: Because of the high number of chemical and organic processes occurring in any wastewater treatment plant, adequate levels of oxygen must be maintained to ensure worker safety. Oxygen sensors should be located in enclosed areas, wherever oxygen levels may be in question.
Purifying Chemicals: Chemicals such as ammonia , ozone and chlorine are all used in the decontamination of water, both in waste water and water purification plants.
Pulp & Paper
Pulp and paper mills can present many dangerous situations, which can be significantly decreased by utilizing continuous gas monitoring.
The chemical pulping technique in the Kraft process utilizes a combination of heat and liquor (chemicals) to delignify wood and reduce it to pulp. Reduction of the wood to pulp takes place in stages, but the heart of the process is in either batch or continuous digesters. It is here that hazardous gases such as hydrogen sulfide and mercaptan are released due to the chemical reaction between the wood chips and liquors.
Pulp stock from the digesters is washed and screened and then sent through the bleaching process. Bleaching is associated with whiteness or brightness, as it is referred to in the pulp and paper industry. Normally it consists of an oxidation process, wherein oxygen is used to dissolve unwanted colored components. In pulp bleaching, oxidation is used to break down lignin molecules, but also to bleach out the dark spots created by non-cellulose components of wood, such as resins, or foreign matter in the pulping process.
Brightness is also obtained by dissolving the lignin molecule through chlorinating. Its removal makes the remaining cellulose fibers appear white to the eye. Bleach chemicals used in this process are chlorine and chlorine dioxide most frequently, and oxygen, peroxide and ozone used as alternatives. Sulfur dioxide is also a concern in the primary bleaching process.
In Kraft mills, the chemicals used are recycled for use throughout the mill. The recovery process is integrally connected to the boilers and power production. All chemicals are recovered through the burning of black liquor (liquor which has already been through the digestive process) in the recovery boiler. Heat released by the oxidation of liquor is used to produce steam for use throughout the plant. Monitoring of hydrogen sulfide gas should be a priority in these locations.
Mining
Depending on the type of mining, the requirements for gas detection can vary greatly, however, there are five main sources of hazardous gas in mining applications.
1. Gases from Blasting:
Gases resulting from blasting are principally carbon dioxide, nitrogen and steam. However, toxic gases including carbon monoxide and nitrogen dioxide also result. As oxygen is consumed in any such blast, oxygen deficiency may also be a result.
2. Methane from Coal Beds:
Highly combustible methane (CH4) or firedamp, as it is called in many coalfields, is formed in the latter stages of coal formation, and because of the depths and pressures, it becomes imbedded in the coal. As excavations are made, methane gas is liberated into the air. Gas is emitted not only from point of excavation, but also from the coal being transported to the surface.
3. Vehicle Exhaust:
As with any other vehicle exhaust application, toxic fumes are a result of the operation of internal combustion engines. In mining diesel vehicles are used primarily, and carbon monoxide and nitrogen dioxide , as well as oxygen deficiency are of concern.
4. Underground Explosions and Fires:
Even small, smoldering fires can create toxic gases including carbon monoxide and nitrogen dioxide, and also consume enough oxygen to cause asphyxiation.
5. Drilling into Stagnant Water:
Pockets of stagnant water can contain large amounts of hydrogen sulfide resulting primarily from the breakdown of pyrites.
Because of the diversity of mining applications, any or all of the sources listed above may contribute to air quality issues, and your application should be looked at on an individual basis to determine which hazards may apply.
Brewing and Bottling
Carbon dioxide (CO2) is a by-product of the fermentation process, as well as being used in carbonation. Carbon dioxide leaks could result in over exposure to employees, as well as possible product damage.
Ammonia and other refrigerants are commonly monitored to detect for leaks in chillers and refrigeration systems. For more detailed information regarding refrigeration gas detection please see our refrigeration application page.
Warehouse forklifts powered by propane or liquefied natural gas present a two-fold hazard, in that leaks of these products can prove catastrophic because of their explosive nature and, toxic carbon monoxide is an exhaust by-product of these machines and if not properly ventilated, it can prove deadly. Nitrogen dioxide is often monitored in areas where diesel trucks are present, like loading docks.
Forklifts powered by electricity may also prove hazardous due to the highly explosive hydrogen given off when batteries are recharging. For more information, see our battery room application.
Gas Properties
Carbon Monoxide
Gas Name: Carbon Monoxide
Chemical Formula: CO
Synonyms: Carbon Oxide, Flue Gas
Product Uses/Sources/Applications
Carbon monoxide is a byproduct of the burning of hydrocarbons. It is a toxic component of vehicle exhaust, and can typically be found in any space where engines are burning gasoline, propane, diesel fuel, natural gas, kerosene, or jet fuel.
Typical carbon monoxide detection applications include installing gas detection equipment in enclosed parking structures, ambulance bays, fire halls, warehouses, loading docks, ice arenas, maintenance facilities and municipal works garages.
Carbon monoxide can also result as a byproduct of malfunctioning heating appliances (furnaces, boilers, stoves, direct and indirect fired air handlers).
Hazards
Toxicity
Short Term (15-minute STEL*) – 100 ppm
Long-term (8-hr TWA*) – 25 ppm
Flammability
Lower Explosive Limit (LEL) 12.5 % in air
NIOSH Pocket Guide Click here for link
Physical Properties
Appearance and Odour odourless, colourless
Relative density (air = 1.0) 0.967
Ammonia
Gas Name: Ammonia
Chemical Formula: NH3
Synonyms: Anhydrous Ammonia, R717
Product Uses/Sources/Applications
Ammonia is used in its gaseous, liquefied, and aqueous forms in a number of applications including:
- Refrigerant (R717) – used extensively in food processing applications and ice rink applications
- A main component in the production of commercial fertilizer
- Used extensively in the production of commercial and household cleaning products
- Pharmaceutical production
- Papermaking: pulping and coating
- Rubber production
Hazards
Toxicity
Short Term (15-minute STEL*) – 35 ppm
Long-term (8-hr TWA*) – 25 ppm
Flammability
Lower Explosive Limit (LEL): 15% by volume
NIOSH Pocket Guide Click here for link
Physical Properties
Appearance and Odour Colorless gas with an irritating, pungent odor
Relative density (air = 1.0) 0.597
Nitrogen Dioxide
Gas Name: Nitrogen Dioxide
Chemical Formula: NO2
Product Uses/Sources/Applications
Nitrogen dioxide is a byproduct of the burning of hydrocarbons. It is a found primarily as a toxic component of vehicle exhaust in any space in which engines are burning gasoline, propane, diesel fuel, propane, natural gas, kerosene or jet fuel. Areas include enclosed parking structures, ambulance bays, fire halls, warehouses, loading docks, ice arenas, maintenance facilities and municipal works garages.
Nitrogen dioxide (NO2) is one of a group of highly reactive gasses known as “oxides of nitrogen,” or “nitrogen oxides (NOx).” Other nitrogen oxides include nitrous acid and nitric acid. While EPA’s National Ambient Air Quality Standard covers this entire group of NOx, NO2 is the component of greatest interest and the indicator for the larger group of nitrogen oxides. NO2 forms quickly from emissions from cars, trucks and buses, heavy construction, and off-road equipment.
For vehicle exhaust detection applications, there are a wide array of hazardous chemicals, including particulates, sulfur compounds, carbon monoxide, carbon dioxide and oxides of nitrogen. As it is not practical to monitor for all of these compounds, a combination of nitrogen dioxide and carbon monoxide sensors will give the best indication of overall air quality.
Hazards
Toxicity
Short Term (15-minute STEL*) – 5ppm
Long-term (8-hr TWA*) 1 ppm
Flammability
Lower Explosive Limit (LEL): n/a
NIOSH Pocket Guide Click here for link
Physical Properties
Appearance and Odour reddish brown gas with a pungent odour
Relative density (air = 1.0) 2.62
Hydrogen Sulfide
Gas Name: Hydrogen Sulfide
Chemical Formula: H2S
Synonyms: Sewer Gas; Sour Gas
Product Uses/Sources/Applications:
Hydrogen sulfide is created during the decomposition process and occurs naturally in natural gas. Gas detection equipment or gas sensors should therefore be deployed in:
- Pulp and paper processing
- Waste water treatment
- Hydrocarbon extraction and processing
- Mining
Hazards
Toxicity
Short Term (10-minute TWA – 20 ppm
Long-term (8-hr TWA) 10 ppm
Flammability
Lower Explosive Limit (LEL): 4.3% by volume
NIOSH Pocket Guide Click here for link
Physical Properties
Appearance and Odour Colourless with an offensive odor described as that of rotten eggs.
Relative density (air = 1.0) 1.188
Sulfur Dioxide
Gas Name: Sulfur Dioxide
Chemical Formula: SO2
Synonyms: Sulfurous Acid Anhydride, E220
Product Uses/Sources/Applications
Sulfur dioxide is a gas which is used in a number of applications including:
- Preservative – particularly for dried fruits
- Anti-microbial and antioxidant in winemaking
- Bleaching agent for paper and textiles
- Neutralizing agent for chlorine in water and waste water facilities
- Until the development of HFCs and CFCs, sulfur dioxide was used extensively as a refrigerant, particularly in home refrigerators
Hazards
Toxicity
Short Term (15-minute STEL*) – 5ppm
Long-term (8-hr TWA*) 3 ppm
Flammability
Lower Explosive Limit (LEL n/a
NIOSH Pocket Guide Click here for link
Physical Properties
Appearance and Odour Colorless gas with an irritating, pungent odor
Relative density (air = 1.0) 2.263
Combustibles
Gas Family: Combustible Gases
We offer gas detection and gas sensors for a wide range of hydrocarbons and inorganic compounds for which the primary hazard is flammability/combustibility.
Product Uses/Sources/Applications
- Gas sensors and gas detection for fuel used in vehicles, heating units, and industrial processes (methane, propane, hydrogen, gasoline, etc.)
- A by-product of processes involving the breakdown of organic matter (waste water treatment , pulp & paper , etc.)
- As a naturally occurring compound within the earths crust (methane). It is extremely hazardous and gas detection and sensors can be used in underground mining applications, especially in, but not limited to coal facilities, as it may be present in almost any mining application
- In oil and gas drilling, production and transportation
- Wherever multiple batteries are being charged (underground telephone switching systems, large UPS, warehouses with electric forklifts, golf cart charging areas, etc.), hydrogen is produced
Hazards
Toxicity
Some combustible gases such as carbon monoxide, ammonia, etc., are both highly toxic and combustible. Strategies for monitoring for such gases should be determined on an application by application basis.
Flammability
Flammability is measured in Lower Explosive Limit (LEL) and Upper Explosive Limit (UEL). The LEL represents the minimum amount of gas (by volume in air) which is required to promote combustion. See chart below:
Combustible Gas |
LEL (%Vol of Gas in Air) |
Relative Density (Air = 1) |
| Acetone | 2.50 | 2.0 |
| Acetylene | 2.50 | 0.9 |
| Ammonia | 15.00 | 0.6 |
| Butane | 1.90 | 2.0 |
| Carbon Monoxide | 12.50 | 1.0 |
| Ethyl Acetate | 2.00 | 3.0 |
| Ethyl Alcohol | 3.30 | 1.6 |
| Gasoline | 1.40 | 3-4 |
| Heptane | 1.05 | 3.5 |
| Hexane | 1.10 | 3.0 |
| Hydrogen | 4.00 | 0.1 |
| Isopropyl Alcohol | 2.00 | 2.1 |
| Methyl Ethyl Ketone (MEK) | 1.40 | 2.5 |
| Methane | 5.00 | 0.6 |
| Methyl Alcohol | 6.00 | 1.1 |
| Octane | 1.00 | 3.9 |
| Pentane | 1.50 | 2.5 |
| Propane | 2.10 | 1.6 |
| Toluene | 1.10 | 3.1 |